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Biomedical subjects

J M Ribó

Publications and source records attributed to J M Ribó.

15 recordsLinked to original sources
PubMed2001

Point-dipole approximation of the exciton coupling model versus type of bonding and of excitons in porphyrin supramolecular structures.

The application of the exciton coupling model to interacting porphyrin chromophores is discussed. Covalently bonded systems and ionic or electrostatically bonded homoassociates require different orientations of the transition dipole moments in order to explain the experimental results: according to the symmetry of the assembly for covalently bonded porphyrins, and assuming isolated chromophores for ionic bonded porphyrins. Further, for covalently bonded systems, an extended exciton coupling has been demonstrated, but the ionic systems are in agreement with non-extended couplings. The relation of these facts to a molecular description of solid-state Wannier-Mott or Frenkel excitons is briefly discussed.

Journal Article↗
PubMed2001

Chiral sign induction by vortices during the formation of mesophases in stirred solutions.

Achiral diprotonated porphyrins, forming homoassociates in aqueous solution, lead to spontaneous chiral symmetry breaking. The unexpected result is that the chirality sign of these homoassociates can be selected by vortex motion during the aggregation process. This result is confirmed by means of circular dichroism spectra. These experimental findings are rationalized in terms of the asymmetric influence of macroscopic forces on bifurcation scenarios and by considering the specific binding characteristics of the porphyrin units to form the homoassociates.

Circular Dichroism↗
PubMed2001

Stirring effects on the spontaneous formation of chirality in the homoassociation of diprotonated meso-tetraphenylsulfonato porphyrins.

Homoassociates of the achiral title porphyrins in acid solutions show spontaneous symmetry breaking, which can be detected by circular dichroism (CD). The CD spectra are due to differential scattering and differential absorption contributions, the relative significance of which is related to the shape and size of the homoassociate. When an earlier model, designed for the association of these diprotonated porphyrins (J aggregates with the geometry of stepped sheets of intramolecular-stabilised zwitterions), was applied to an exciton-coupling point-dipole approximation, the folding of the one-dimensional homoassociates explained the CD signals detected. An effect of the vortex direction, caused by stirring or rotary evaporation, upon the exciton chirality sign was detected. In the case of H2TPPS3, the number of experiments performed gave a statistical significance to this effect. This vortex effect can be attributed to enhancement of the chirality fluctuations that originate in the diffusion-limited aggregation to high-molecular-weight homoassociates. In this sense, the phenomenon could be general for supramolecular systems that are obtained under kinetic control, and its detection would be possible when inherent chiral chromophores were being generated in the association process.

Journal Article↗
PubMed2001

[Laparoscopic splenectomy in the treatment of hematologic diseases].

Laparoscopic approach to surgical procedures in children is used in different diseases, but there are some controversies for using this technique in the splenectomy. Laparoscopic surgery decreased pain, postoperative ileus and the hospital stay; and improve cosmetics, the most important disadvantage is the longer operating time. Splenectomy is indicated more in immune thrombocytopenic purpura (PTI) and hereditary espherocytosis (HE). We review our experience in laparoscopic spelenectomy.

Adolescent↗
PubMed2000

Application of focused-microwave wet digestion to the determination of trace metals in human gallstones by ICP/AES.

We propose an analytical digestion method for trace metal determination (Co, Cr, Cu, Fe, Mn, Ni and Zn) in gallstones, in an attempt to facilitate detection of their origin. The method consists of sample digestion with HNO3 and H2O2 by means of focused microwave. Metals are quantified by inductively coupled plasma atomic emission spectroscopy. The effect of calcium concentration in the analytical solutions was studied. Cu, Fe, Mn and Zn were detected in all the samples analysed and the highest concentrations were obtained for Cu and Fe, especially in black-pigmented gallstones. The reproducibility in terms of %RSD, determined in the gallstones with the lowest metal content, was below 5% for Cu, between 10% and 15% for Mn and Zn and up to 25% for Fe.

Calcium↗
PubMed1997

[Laparoscopic Nissen fundoplication in children with encephalopathy].

Conventional management of gastroesophageal reflux (GER) and hiatus hernia in children affected with encephalopathy can deteriorate their pulmonary function, already compromised by their leaning position and their spine deformations. The results after laparoscopic surgery for GER in 6 encephalopathy children are reviewed; their ages ranged from 9 to 14 years, their accompanying diseases were: spastic tetraparesia, hydrocephalus, scoliosis, epilepsy and Reye's syndrome. The laparoscopy procedures followed the same surgical steps as open surgery; the surgical time was 3 to 5 hours; the average hospital stay was 3 days. Oral intake started 8 hours after surgery. The successful results of these first cases in this group of patients with neurologic anomalies, suggest that laparoscopic Nissen funduplication is the treatment of choice for GER and hiatus hernia.

Adolescent↗
PubMed1996

Apolipoprotein E polymorphism and gallstones.

BACKGROUND & AIMS: Apolipoprotein (apo) E is a genetically polymorphic protein influencing lipoprotein metabolism and the risk of both atherosclerosis and Alzheimer's disease. As opposed to common apo E3, apo E2 decreases and apo E4 increases hepatic lipoprotein uptake; hence, apo E4 could promote gallstone formation by increasing hepatic and biliary cholesterol concentrations. This study was designed to evaluate whether apo E polymorphism is related to gallstone risk. METHODS: apo E phenotype was determined in subjects older than 40 years of age (160 with and 125 without gallstones) and in 61 patients with cholesterol gallstones who underwent cholecystectomy. Bile composition, nucleation time, and gallstone features were analyzed in surgical patients. RESULTS: The E4/3 phenotype was enriched in both patients with gallstones and those who underwent cholecystectomy, with significantly (P < 0.006) higher epsilon 4 allele frequencies than in gallstone-free subjects (odds ratio, 2.67 [95% confidence limits, 1.23-5.93] and 3.62 [95% confidence limits, 1.49-8.91], respectively); women, but not men, accounted for these differences. The prevalence of the epsilon 4 allele increased with age in patients with gallstones, whereas the opposite occurred in gallstone-free subjects. Biliary lipid and gallstone cholesterol content tended to increase in the sequence E4 > E3 > E2 in patients who underwent cholecystectomy. CONCLUSIONS: Carrying the apo E4 isoform is a genetic risk factor for cholelithiasis in humans, thus adding another adverse effect of apo E polymorphism on health.

Adult↗
PubMed1994

The antioxidant role of bile pigments evaluated by chemical tests.

Bilirubin, biliverdin and their serum albumin complexes were tested as oxyradical scavengers (superoxide generated by the xanthine/xanthine oxidase system and peroxyl radical-trapping antioxidant ability). As superoxide scavengers the free bile pigments showed activities near to that of serum albumin, higher than the water soluble vitamin E analog Trolox and lower than ascorbic acid. The peroxyl radical-trapping antioxidant abilities of the tested bile pigments were much higher than those of the serum albumin and of the same order as their serum albumin complexes. This interaction with peroxyl radicals showed different stoichiometric factors for bilirubin (approximately 2) and biliverdin (approximately 4).

Animals↗
PubMed1994

[Obstructive candidiasis: a process with surgical solution].

We describe three severe clinic cases due to fungus balls of Candida albicans in hospitalized risky patients which presented a quickly clinical evolution. Because of their different local presentations medical and surgical management was needed. In the first case a intestinal fungus ball was found whereas in the other two cases were localized in the urinary tract. Here we present their clinical findings rather than their evolution after a medical and surgical management.

Adolescent↗
PubMed1990

Proton-induced dismutation of superoxide in aprotic media by bile pigments.

Cyclic voltammetry of molecular oxygen in aprotic media (dimethylformamide) and in the presence of bilirubin and other bile pigments shows that superoxide anion (O2-.) undergoes proton-induced dismutation. Lactam hydrogens of bile pigments are sufficiently acid to induce (O2-.) disproportionation to O2 and H2O2. Because of its characteristic lipophilic behavior, a biological role for natural bilirubin similar to that of other non-enzymatic lipophilic scavengers of (O2-.) is suggested.

Bile Pigments↗
PubMed1989

[Role of somatostatin in the treatment of intestinal fistulas].

Somatostatin is a peptide hormone which inhibits the secretion of the growth hormone, and has proved to be a powerful inhibitor of exocrine pancreatic, gastric and intestinal secretion. It was therefore used as an adjuvant therapy in the conservative treatment of two children of eight and nine years old with fistulas of the small intestine. The first case was a colonic fistula for cecal defect, surgical intervention was carried out because treatment during 14 days with hormonal treatment after the third consecutive day of somatostatin application. In this study the authors present their experience with somatostatin, with particular emphasis on the indications contraindications, doses and lines for administration.

Abdominal Neoplasms↗
PubMed1986

Utility of biliary microscopy for the prediction of the chemical composition of gallstones and the outcome of dissolution therapy with ursodeoxycholic acid.

To learn whether microcrystalline solids in bile could predict gallstone composition, the findings determined by polarizing microscopy of gallbladder bile were related to stone type at cholecystectomy in 53 patients. Cholesterol crystals were present in 36 of 39 cholesterol stone bile and absent in 12 of 14 bile from non-cholesterol stones. Fifteen cholesterol stones (eight radiopaque) contained calcium carbonate, and characteristic vaterite microspheroliths were observed in 53% of their bile. In another study, crystals in basal duodenal bile were related to the outcome of gallstone dissolution treatment with ursodeoxycholic acid, 10 mg/kg X day. In 39 patients treated for 1 yr, efficacy (complete gallstone dissolution) was 41% overall and 52% in patients with stones less than or equal to 10 mm in diameter. In connection with the findings of biliary microscopy, efficacy was 93% in 14 patients with cholesterol crystals in bile, and 27% in 11 patients with microspheroliths in bile. Cholecystectomies in 9 patients with dissolution failure revealed 4 cases of non-cholesterol stones and 5 cases (including 3 with on-therapy calcification) of calcium carbonate-rich cholesterol stones with a surface/interior mineral ratio greater than 3. The results confirm that cholesterol crystals in bile are a sensitive measure of cholesterol gallstones. They also show that vaterite microspheroliths in bile indicate the presence of calcium carbonate in gallstones. Both findings suggest that biliary crystals reflect gallstone composition, and it is demonstrated that this information is useful in predicting the success or failure of cholelitholysis with ursodeoxycholic acid. Finally, the data show that radiologically undetectable stone calcification reduces the probability of dissolution, and that the calcified structures appearing in some stones during treatment are composed of calcium carbonate.

Bile↗
PubMedDate not supplied

[Thymectomy in juvenile myasthenia gravis].

INTRODUCTION: Juvenile myasthenia gravis (JMG) is an infrequent autoimmune disease, the symptoms and therapeutic handling of which do not differ from those of the adult forms. Chronic treatment with corticoids very often causes side effects in childhood, which is why patients are being submitted to thymectomies at younger ages with better results. AIMS. To analyse the clinical and evolutionary profile of JMG treated by thymectomy in our centre. PATIENTS AND METHODS: We report the case of four girls aged between 5 and 13 who were diagnosed as suffering from generalised myasthenia gravis (MG) with bulbar affectation. One of them started with a myasthenic crisis. The four of them were submitted to Tensilon s test, an electrophysiological study, determination of AChR, thoracic CT, and study of autoimmunity and thyroid functioning. After surgery the thymus was analysed histologically. RESULTS: They all gave positive in Tensilon s test and were seropositive for AChR. They were treated with anticholinesterases, up to the maximum tolerated dose, and corticoids, without complete remission being accomplished and so they were submitted to a thymectomy in the first year of evolution. In three cases surgical approach was transsternal and in the other by means of a videothoracoscope. All the thymuses showed lymphoid hyperplasia. After a variable follow up the girls are at present asymptomatic, although none of them has been able to completely give up the pharmacological treatment. CONCLUSIONS: Thymectomy is one of the mainstays of treatment for JMG. The ever more frequent use of videothoracoscopic techniques achieves results that are similar to those obtained by conventional surgery but with fewer post operative and aesthetic problems

Adolescent↗
PubMedDate not supplied

[Risk factors in cerebrovascular disease. Do transient ischemic attacks lead to changes in lifestyle?].

A minor stroke does not cause sufficient alarm in patients to change their lifestyles. 46 patients who suffered strokes in the previous 2 years were contacted by telephone, recording rehabilitation programs, medical therapy and modification of dietary habits. It was discovered that only 50% of those requiring motor rehabilitation actually received such treatment; and only one of twenty carried on speech exercises. Subsequent ischemic events were reported by 22 patients: 12 of whom had strokes, 8 ischemic myocardial attacks and two patients suffered both conditions. The majority of patients followed the prescribed medical treatment and advice badly. Of the 46 patients reviewed, 31 were hypertensive and only 16 follow recommended diets. Out of 15 smokers only, 6 gave up, and from 21 with dislypemia only 10 modified their diets. Of all patients only the most severely affected complied satisfactorily to medical treatments; a possible explanation for this would be that the contact between patients and physician (neurologist and family doctors) was discontinued immediately after the patients discharge from hospital. It is recommended therefore that steps be taken to insure better communication between neurologist, general practitioner and patient; thereby improving prognosis.

Adult↗